Specialized baby bottles are manufactured with features that are designed to attempt to reduce colic symptoms in infants drinking from the bottles, particularly from zero months to approximately four months. Typically, a vent insert used in conjunction with the bottle top provides a passage for air from the exterior of the bottle to the interior of the bottle. In these bottles, bubbles of air travel through the drinking liquid or an anti-bubble tube must be provided in order to transfer the air from the top of the bottle to the bottom of the bottle (which is higher than the top while the baby is drinking). These top vent systems have dispensing openings for the passage of liquid therethrough for dispensing.
For ease of internal cleaning and in order to eliminate the necessity for an anti-bubble tube, various bottles were developed having bottom openings to permit the inflow of air therethrough during drinking. One such baby bottle is shown in U.S. Pat. No. 3,134,495. This bottle includes two nipples and two threaded retainers, one mounted outside the top opening for dispensing and the second mounted inside the bottom opening for venting. Both threaded retainers have apertures in the middle to permit the outflow of liquid and the inflow of air, respectively. This bottom air receiving aperture, while it can be small, can result in dirt entering into the bottle together with the ambient air and the aperture can be difficult to clean to prevent clogging.
Another such baby bottle is shown in U.S. Pat. No. 5,499,729. This bottle includes a diaphragm member disposed in the bottom opening and covered by a cap with a central hole. The diaphragm member is gas and liquid tight when the inside and outside pressures on the bottle are equal and the bottle is in an upright configuration with the feeding liquid resting on the diaphragm member. The diaphragm member has a central portion which is dome shaped and provided with apertures that are in a sealed shut configuration when the diaphragm member is relaxed yet that are opened directly to the outside of the bottle when the diaphragm member is expanded responsive to differential air pressure. This type of exposed arrangement can result in dirt and germs collecting on the diaphragm and, during use, entering into the bottle together with the ambient air. In addition, bottom holes can result in clogged air inlet apertures.
Unlike conventional top vent systems, openings for passage of liquid for dispensing are not relevant for bottom venting systems.
Accordingly, there is a long felt need for a baby bottle having a vent system that does not require holes in the bottom closure of the bottle for the ingress of ambient air, so is less susceptible to the entry of dirt together with the ambient air, and it would be desirable to have a practical vent system that can be used to seal and vent the bottom of any liquid container for dispensing a liquid that has a bottom opening and that does not require holes in the bottom closure.